Abstract

PURPOSE:

We previously showed that 75% of radiation therapy (RT) failures in patients with unresectable esophageal cancer are in the gross tumor volume (GTV). We performed a planning study to evaluate if a simultaneous integrated boost (SIB) technique could selectively deliver a boost dose of radiation to the GTV in patients with esophageal cancer.

METHODS AND MATERIALS:

Treatment plans were generated using four different approaches (two-dimensional conformal radiotherapy [2D-CRT] to 50.4 Gy, 2D-CRT to 64.8 Gy, intensity-modulated RT [IMRT] to 50.4 Gy, and SIB-IMRT to 64.8 Gy) and optimized for 10 patients with distal esophageal cancer. All plans were constructed to deliver the target dose in 28 fractions using heterogeneity corrections. Isodose distributions were evaluated for target coverage and normal tissue exposure.

CONCLUSIONS:

The use of SIB-IMRT allowed us to selectively increase the dose to the GTV, the area at highest risk of failure, while simultaneously reducing the dose to the normal heart, lung, and liver. Clinical implications warrant systematic evaluation.

(top row) Axial, sagittal, and coronal views of a 2D-CRT plan to deliver 50.4 Gy to a patient with esophageal cancer, similar to the plans used in Intergroup 0123. (bottom row) A modern plan for delivering 50.4 Gy as intensity-modulated radiation therapy to the same patient with esophageal cancer.

(top row) Axial, sagittal, and coronal view of a 2D-CRT plan to deliver 50.4 Gy to a patient with esophageal cancer (similar to the plans used in Intergroup 0123). (bottom row) Simultaneous integrated boost IMRT plan with the gross tumor volume being treated to 64.8 Gy and the planning target volume to 50.4 Gy.

Dose volume histogram of an individual patient comparing an a 2D-CRT plan (dashed line) to 50.4 Gy (similar to that used in Intergroup 0123) to a simultaneous integrated boost (SIB)-IMRT plan (solid line) in which the gross tumor volume is treated to 64.8 Gy and the planning target volume to 50.4 Gy. The SIB-IMRT plan increased the mean GTV dose by 28% (p = 0.001) and decreased the mean heart dose by 30% (p = 0.001), the mean total lung dose by 23% (p = 0.007), and the lung V20 by 37% (p = 0.004).